Introduction

Residual migration is the process of updating an image without re-running the entire migration process. Its main application is in refining of velocity models. Rosales et al. 2001 first introduced Stolt residual migration for converted waves (PS).

Stolt migration is a constant velocity process. Although Stolt residual migration is also based on the assumption of constant velocity, Sava 2000 shows that Stolt residual migration is valid in variant velocity media, since the residual migration operator depends only on the ratio between the migration velocity and the real velocity.

For converted waves, Stolt residual migration basically depends on the combination of three out of four parameters: 1) The ratio between the migration and the real P-velocity ($\rho_p$), 2) the ratio between the migration and the real S-velocity ($\rho_s$), 3) the ratio between the P and S migration velocities ($\gamma_0$) and 4) the ratio between the real P and S velocities ($\gamma$).

Understanding how these parameters interact and affect PS residual migration in a non-constant velocity medium is of crucial importance for future velocity analysis studies. I present residual migration results on a 2D line extracted from the 3D OBC data set of the Alba field after geometry regularization Rosales and Biondi (2002).